[rules-users] Use of a DAO in LHS

Hello, I have a DRL file in which I have a global variable representing a DAO. So, I succeed in writting a rule which uses this DAO to run a SQL query on the database from the RHS part. But now, I would like to use my DAO in the LHS, I mean I want to fire my rule only if a condition is ok on the result of my SQL query. Is it possible to call a method of my DAO in the LHS part ? I have not found an example. Thanks. Regards, Jean-Baptiste